[GRASSLIST:2332] i.his.rgb

[Ian Macmillan]

Hi all, I have a problem that I can't quite figure out with i.his.rgb.  I have
been manipulating landsat 7 data using the method described in the GRASS book. 
I am trying to add in band 8.  So far I can get this to work, in a number of
different ways.  The way I have found to be the most successful (for retaining
the colors that I want) is to enhance the contrast of all 4 bands using
r.rescale, converting to his (i.rgb.his), and converting back to rgb (i.his.rgb
with band 8 as intensity).  The problem is that a lot of "holes" appear in the
final rgb files.  Single pixels seem to be converted to a value of zero, even
though the same pixels (in space) are not zeros or nulls in the original files
(pre i.rgb.his > i.his.rgb).  I have posted a specific example here.  

www.uweb.ucsb.edu/~ian_macmillan/hisrgb.jpg

Band1x is the i.his.rgb converted blue file, while bands 1,2,3,8 are the
original rescaled files.  The black dots are clearly visible scattered
throughout the image.  They each have a value of zero.

Anybody have any ideas what is going on?

thanks, Ian